The invention relates to portable and personal-sized electric air humidifiers, more particularly to an improved warm air humidifier.
Air humidifiers are important in controlling the environment in homes during very dry weather, or in winter whenever outside air of low temperature is drawn inside and heated, causing the relative humidity in the home to be lowered to an uncomfortable degree.
Portable humidifiers are well known in the art, and may be classified in the following paragraphs.
1. Steam generators which comprise a water container and an electric heating element submerged in the water. Safety devices are provided for switching off the current as soon as the water level drops below the heating element. Since a flow of hot steam is blown directly into the room to be humidified, there is always the danger of a person, especially a child being scalded whenever he or she comes into contact with the jet of steam ejected, typically, at a temperature of about 212.degree. F. Furthermore, since all of the water is heated, the container of hot water, when overturned, may cause serious injuries to persons nearby. PA1 2. Porous medium humidifiers generally include a porous medium structure partly submerged in cold water contained in an open vessel and a blower unit drawing air through the porous medium structure. The porous medium may be in the shape of a disc or a dram with part of the medium dipping into the water, which is slowly rotated while air is blown through the portion above the water level, thus carrying humidity into the room. The porous medium may also be in the form of a stationary body adapted to draw water into the upper non-immersed part by capillary action, from where it is carried into the room by air blown therethrough. PA1 3. Ultra-sonic humidifiers generally comprise a container filled with water which is brought to a vibration by high-frequency vibrator means which causes the water to be atomized. An air stream directed onto the water surface carries the mist into the room to be humidified. PA1 1. The high velocity jet stream from the nozzle, while flowing through the "still air" in the ejector tube, will cause air next to it to move with it through the exertion of a shear-force. That moving air then will carry along with it the adjacent layers of air particles, which in turn carry adjacent layers until the boundaries of the tube are reached. By properly designing and dimensioning and positioning the relevant components involved, entrainment of air with steam to provide a desired ratio of air to steam and temperature may be obtained. PA1 2. The negative or low pressure created within the steam ejector tube, which is dependent upon the dimensions of the "draft" of the tube, will influence the flow of the air to be treated into the humidifier, especially where provision must be made to overcome the pressure drop occasioned by reason of the air having to flow through a filter medium when the humidifier is to remove particulates from the air to be treated. PA1 3. A "buoyancy" phenomenon is utilized in the present invention. As the steam mixes with the air the mixture becomes warm and humid, thus attaining a specific gravity lower than the surrounding dry cooler air. Consequently, the air steam mixture adds another driving component to the flow of the mixture and rises through the tube to enhance the drawing in of fresh or cool air from the bottom of the tube, much as in the well known "atmospheric hyperbolic" cooling towers.
The major drawback of both porous medium humidifiers and ultra-sonic humidifiers is that the water staying in the container is not heated to its boiling point as in the steam generator and, is therefore susceptible to the growth of micro-organisms which are subsequently carried by the air stream into the room where it may be ingested by people.
Warm-air humidifiers share the benefits of steam generators in that growth of micro-organisms is forestalled by heating the water to its boiling point. Also, warm-air humidifiers avoid the drawback of hot steam entering the room, since in this type of humidifier the steam is carried into the room as a mist mixed with air, at a temperature to be selected by judiciously choosing the ratio of steam and air.
A typical warm-air humidifier is described in U.S. Pat. No. 4,564,746. It includes a heated evaporation chamber which is enclosed to prevent leakage or damage and a fan adapted for dispersing the generated steam into the room via a cabinet passageway. The evaporation chamber is mounted on tracks which permits it to be slid out of its enclosure for cleaning and servicing. The heating element, which is operationally enclosed in the chamber, is attached to a cover which is likewise movable out of the humidifier cabinet for cleaning and servicing.
Unfortunately, the design of this humidifier is relatively intricate and expensive. The heating element is attached to a movable cover which is provided with flexible tubing and must be moved upwards on vertical tracks to clear the top of the water enclosure, permitting the latter to be slid out sideways. This requires a significant amount of space and cannot be serviced except by a skilled person.
In the present invention, a steam ejector is provided which takes the place of the motor driven blower.
Humidifiers employing the motor driven blowers, such as is found in U.S. Pat. No. 5,014,338 and in patent application Ser. No. 07/606,938 have many benefits and advantages. On the other hand, the use of warm air humidifiers utilizing motor driven blowers have some disadvantages. When used in nurseries and in bedrooms such humidifiers are non-conducive to sleep because of the mechanical and aerodynamic noise associated with motor driven blowers. In addition, the presence of high humidity to which motor shafts are exposed creates rusting problems with binding of the shafts to the bearings often resulting. Obviously, this creates expensive maintenance problems.
Certain criteria are desired in warm air humidifiers to maximize the desirability and efficiency of such devices for the user. One criterion is to maintain the steam-air mixture at a predetermined temperature which ranges between 37.degree. C. and 65.degree. C. (99.degree. F.-149.degree. F.) where the lower end of the range approximates human body temperature and the upper end represents a value at which the steam air mixture still may be brought into contact with a person without the sensation of pain. Another criterion is to provide a uniform mixing of air and steam resulting in an even temperature profile at the outlet grille and avoiding non-uniform degrees of air saturation as well as local recondensation on portions of the grille.
Accordingly, an object of the present invention is to provide an improved and novel non-motor driven warm-air humidifier which utilizes a simple and inexpensive structure and still obtains results equivalent to, or better than, those obtained by humidifiers employing motor driven blowers.
Another object is to provide an improved and novel humidifier which provides for the proper and uniform mixture of steam laden air having the proper ratio of air and steam and substantially uniform temperature profile at the outlet grille.
A further object is to provide an improved and novel humidifier which employs a steam ejector in place of a motor driven blower and which exhibits significantly less objectionable noises than those employing motor driven blowers.
A still further object is to provide a novel and improved humidifier which utilizes a steam ejector tube having a restricted throat portion therein and which is dimensioned and positioned in relation to a steam nozzle in which steam flows at a certain velocity and produces a steam air mixture of the proper saturation and temperature substantially noise free or of minimum noise.
Another object is to provide a novel and improved gravity water-feed humidifier in which the constant pressure to drive the generated steam through a steam nozzle is maintained by a differential head of water existing between the steam generation compartment and the water supply compartment.
A still further object is to provide a compact, self contained, personal-size warm air humidifier having the above advantages.
Further objects and advantages of the present invention will be apparent to one skilled in the art in the following description of the invention and the claims.